Subject:	Extension tubes are not teleconverters! (+)
Author:	drdread
Date:	2/18/2002 8:58:14 AM
Message:

Be careful here. Whaletale was talking about a teleconverter, which is a completely different item than an extension tube. Teleconverters are complex pieces of optics that let you use AF (among other things). Extension tubes are simple pieces of plastic.

You will not be able to use AF with an extension tube. Your focus point will be fixed at a particular distance from the lens, and your DOF will be minimal. If you get the focus point wrong, your picture will be badly out of focus.

Nikonos users have used extension tubes for macro work for years, so there's lots of experience out there. You might talk to an experienced Nikonos user about the best way to use an extension tube.

Finally, you are incorrect in stating that using an extension tube will not cost you any light. There is an effect called the 'bellows effect' that will change the effective aperture of your lens. You will *definitely* have to account for this when using an extension tube. Of course, if your camera is on auto-exposure, you might have an easier time of it.

Good luck,
D

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